This invention pertains to the aggregation of computer systems and other devices requiring a clock or oscillator and, more particularly, to the mitigation of electromagnetic interference of the aggregation.
Devices that have embedded oscillators or clocks inherently emit electromagnetic energy. The energy is emitted at frequencies related to the fundamental frequency of the oscillator or clock. This emitted energy is both undesirable and parasitic to other devices. The related frequencies can be of any component of the oscillator frequency including the fundamental frequency and any harmonics thereof. The harmonic components of the fundamental frequency occur at multiples of the fundamental and at sums and differences between any two or more components.
Devices which have embedded oscillators or clocks require testing for compliance to several government agenciesxe2x80x9d established requirements. One such agency is the Federal Communications Commission. The established requirements maintain that emissions for any given device remain below a given threshold. The threshold corresponds to an amount of energy per predefined frequency bandwidth which energy could reasonably interfere with a neighboring device. The testing device used in order to determine compliance is usually a spectrum analyzer which sweeps all frequencies of interest and which reports the detected level of emissions per the predefined bandwidth throughout the sweep of frequencies.
Devices are currently produced with a fixed set of one or more oscillators which function as time keepers or clocks. These devices usually take the form of an electronics board assembled in a case with other ancillary parts and creating a working device. As singular elements, each completed device is certified to comply with the defined set of government agency requirements. When clustering and operating more than one of these devices in close proximity, the result is an integrated higher level system. It is this integrated system, the aggregation, when operating, that cannot be expected to meet the original agenciesxe2x80x9d criteria for each of the elements it is composed of. The problem is that the aggregation of systems generally exceeds the allowed energy/frequency levels set by one or more agencies.
An aggregation of devices is provided in which a subset or all of the devices are designed to operate in close proximity of each other. The subset or all of the devices are provided with a programmable oscillator or clock. The devices are linked through an inter-device link. Each proximate device contains a clock frequency controller which couples the inter-device link and the programmable oscillator or clock and which controls the frequency of the programmable oscillator or clock. The frequency of each proximate device is set to operate at a unique operating frequency. Each unique frequency is set to differ from each other by at least a predetermined frequency differential.